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  <script>
    // 使用for循环 - 求出班级里同学们平均年龄[15, 19, 21, 33, 18, 24]
    // 1.数组初始化
    let arr = [15, 19, 21, 33, 18, 24]
    let sum = 0
    // 2.遍历数组
    for (let i = 0; i < arr.length; i++) {
      sum += arr[i]
    }
    let average = sum / arr.length
    alert(`${average}`)
  </script>
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